If you are looking for technical issues related to lost foam casting, design points, or how to apply them on castings, then the following is exactly what you want to see. From the choice of materials to the production of white molds, the process is ultimately.
First of all, about the white mold
In the production of lost foam casting, in addition to those who have a white mold mechanized production foundry, it is a very common production process to use a bonded white mold to enter the lost mold mold in the production of white mold. In production, there are many precautions that require special attention.
1. Selection of materials such as EPS and STMMA.
The quality of the material directly affects the quality of the white mold. Poor quality materials will cause serious carbonation in the production of castings and directly increase the rate of scrap. Poor quality materials, gasification rate during gasification, air pollution is also worse than good quality materials. The gasification speed of the mold and the amount of gas generated will affect the operation of pumping negative pressure. Air pollution directly affects the environmental assessment of foundry companies. These chain reactions are combined and often become unaffordable costs for lost foam foundries.
Therefore, in the selection of materials, we must pay great attention. It is necessary to visit the problem of carbon increase caused by the white mold, and also to avoid the problem of slow gasification of the white mold.
2. In the production of lost foam molds, the mold stress problem should be fully considered.
The mold stress is not only the structural stress of the white mold itself but also the stress generated during the bonding process. There is also an increase in coating stress after brushing the coating. The heat generated during the mold drying process affects the stress.
Solving the problem of mold stress is the primary condition for ensuring the accuracy of lost foam castings.
3, the choice of white mold adhesive
White mold adhesive is an important material for hand-splicing lost molds. It is also the most easily overlooked material in production. Qualified adhesive can not only ensure the bonding of the module, but also reduce the amount of water and reduce the excessive water molecules during casting, thus affecting the quality of the casting.
Five design points of the lost mold
The key to the success of the lost mold design is to understand the importance of close cooperation between the casting manufacturer, the user and the mold designer. The mold designer first meets the requirements of the mold and the needs of the casting factory, and secondly meets the requirements of mold manufacturing and mold forming.
1, casting holes
In other types of casting methods, the casting holes can be obtained by sand cores or by machining (eg drilling). For each casting, whether the casting holes have their corresponding characteristics, but in general, the casting holes The cost of subsequent machining is reduced. The casting holes can be made directly on the mold by special mold design such as using pins, mandrels or other mechanisms.
2, reduce machining allowance
Standardizing the correct EPC mold design can reduce the weight of the casting by reducing the draft and machining allowance. This flexible design is not possible in many other casting methods. It is one of the greatest advantages of the EPC process.
3. Eliminate complex and expensive sand cores
The EPC process eliminates the indispensable sand core in ordinary sand casting. The fixed and movable blocks in the EPC mold form a shape similar to the sand core in the foam model, both in the shape of the sand core.
4. Comprehensive casting design
The parting surface is determined according to the shape of the casting. Generally, the parting surface of the lost foam casting is similar to other casting processes, but in some details it is slightly different: the production designer must work with the mold designer to determine the parting surface. The position of the glued surface and the desired characteristics can reduce the number of model blocks.
5. Sand core characteristics
For castings with grooves, internal cavities, connecting channels or other holes, sand cores are required for other casting methods: in EPC processes, they can be solved by using live blocks or by gluing together the block models.
In the lost foam casting process, the whole process includes seven links, each of which has a great influence on the quality of the lost foam casting. Of course, the casting process is also a vital part of the entire lost foam casting process. Precautions for the casting process, strict control of each detail in the casting process is the key to producing high quality lost foam castings.
The casting process of lost foam casting is a process in which the molten steel is filled and the vaporization of the foam mold disappears. The whole process needs to pay attention to:
(1) The runner should be filled with molten steel from beginning to end. If it is not full, due to the limited strength of the coating layer, the sand collapse and the phenomenon of air intake are easy to occur, resulting in casting defects.
(2) When casting molten steel, be sure to grasp it to ensure stable, accurate and fast. Instantly fill the sprue cup and do it quickly and continuously, and the ton of molten steel is about a minute or so. If the molten steel in the same box castings will suck in the air, it may cause sand-slipping phenomenon or increase the porosity of the casting, resulting in the scrapping of the casting.
(3) Lost foam casting is closed with a negative pressure and must be closed below the pouring cup. The molten steel enters the molding die, and it begins to liquefy and burn, and the gasification disappears. The front end of the molten steel forms a temporary cavity at a short distance, so the speed at which the molten steel is filled is almost the same as the speed at which the foam model disappears. In order to prevent the high temperature radiation of molten steel from melting other models in the same tank, the runner is appropriately farther away from the casting model. The position of the sprue is selected from the lowest position of the full box casting. When pouring, pay attention to adjusting and controlling the vacuum of vacuum in a certain range. After pouring, keep it under a certain negative pressure for a period of time. The negative pressure stops and the molten steel condenses out of the box.